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  • 1.
    Björklund, Glenn
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Sundström, David
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    The effect of speed and gradient on running economy and oxygen uptake during downhill running2019Conference paper (Refereed)
    Abstract [en]

    Downhill running poses challenges were the gradient is of importance for energy cost and oxygen uptake. While demonstrated that downhill running at a slight gradient is most efficient, the energy cost increases with a steeper gradient (1). However, the additional effect of running speed has not been studied for downhill running. Therefore, the aim of the study was to analyse the combined effect of gradient and speed in downhill running on oxygen cost and running economy. METHODS:Runners (n=6) were recruited for the study and performed 1) VO2max and running economy (J·kg-1·m-1) tests and 2) an experimental running protocol at two speeds,12 km·h-1 and 80% of the speed at VO2max (V80) and three gradients (0, -5° and -10°). V80 was higher than 12 km·h-1 for all participants. All testing was performed on a large treadmill 3x5 m (Rodby, Sweden) that were controlled for speed and gradient. The experimental protocol was performed continuously with 5 min at each workload in a randomized order, 30 min in total. VO2 was measured throughout the experimental protocol using a mixing chamber (Moxus Metabolic Cart, USA). RESULTS:VO2 expressed as ml·kg-1·min-1 increased because of speed (F1,5=27.8, p=0.003) and decreased with gradient (F1,5=87.6, p<0.001). Between -5° and -10°, VO2 decreased less during V80 compared to 12 km·h-1 shown by an interaction (F2,10=7.9, p=0.009). However, speed did not influence running economy (F1,5=0.9, p=0.38) while gradient increased running economy (F1,5=90.1, p<0.001). A non-significant interaction effect suggests a shift in running economy between -5° and -10° depending on speed (F2,10=3.5, p=0.07). The running economy at V80 was higher compared to 12 km·h-1 at -5° but reversed at -10°. While a relation between running economy at V80 -10°, V80 -5° and 12 km·h-1 -10° (rs>0.88, p<0.019) was found, no relations between running economy on level terrain and steep downhill running (-10°) were recognised. CONCLUSION:While we found no effect on running economy from speed alone, we did see a shift in the running economy for different speeds at an increased downhill gradient. This indicates that a high speed (V80) is more efficient at moderate downhill gradients, while a lower speed (12 km·h-1) is more efficient in steeper downhill gradients. While previous research demonstrate that gradient is of great influence to running economy, the findings of this study suggest that speed also affects the running economy in downhill running.

  • 2.
    Bäckström, Mikael
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Koptioug, Andrei
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Sundström, David
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    A New Wind Tunnel Facility Dedicated to Sports Technology Research and Development2016In: Procedia Engineering, Elsevier, 2016, Vol. 147, p. 62-67Conference paper (Refereed)
    Abstract [en]

    It is desirable to test sportswear and sports equipment at exactly the same conditions experienced during use. Although outdoor tests are in many cases the most adequate, they are at the same time quite complex, demand special measurement technology and wearable equipment. Results of such tests are often hard to interpret due to large variations because of rapidly varying ambient conditions and individual specifics of human objects, among other factors, which are hard or impossible to control. One common alternative is provided through indoor tests made in a stable, controlled environment. Controlling such parameters as temperature, wind speed and direction, air humidity with indoor facilities intended to replicate ambient conditions, and designed to house large objects, is a complex undertaking. Furthermore, replicating seasonal conditions complicates matters even more. A significant amount of research and development related to the operation of sports and other related equipment at high speeds and windy conditions has been carried out in wind tunnels with different degrees of climatic realism. However, the majority of such facilities are designed and constructed for the automotive industry, the aerospace industry and for marine research. A new wind tunnel facility, opened in March 2015 at the Sports Tech Research Centre at Mid Sweden University, is currently among the very few facilities in the world designed under the direct control of sports technology specialists and dedicated primarily to research and development within sports, outdoor clothing and footwear as well as equipment development and testing. The main goal when constructing this dedicated facility has been to successfully replicate ambient conditions for training and equipment testing in environments with controlled wind speed, temperature (+4 to +35°C) and precipitation (from fine mist to heavy downfall). The wind tunnel facility houses the largest moving belt in Sweden (5 m long and 2.7 m wide) which can be adjusted for leveled, uphill and downhill motion. The moving belt is placed in a 10 m2 test section in which the wind speed can be adjusted to match belt speed or independently up to 55 km/h (without narrowing the test section). A fog and rain system, mounted in the test section, can generate rainy conditions varying from fine mist to heavy monsoon. It is also possible to open the facility in order to allow experiments to be performed in wide range of outdoor, ambient conditions. This paper presents the basic parameters of the new wind tunnel facility. As this facility is open for wider international cooperation, we also report the general directions of current research and the future work planned to be carried out at this facility.

  • 3.
    Bäckström, Mikael
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Koptyug, Andrey
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Wiklund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Sports Technology Education at Mid Sweden University2013In: 6TH ASIA-PACIFIC CONGRESS ON SPORTS TECHNOLOGY (APCST), Elsevier, 2013, Vol. 60, p. 214-219Conference paper (Refereed)
    Abstract [en]

    In present paper we would like to share some experiences of building new education in Sports Technology at MidSweden University and the results of 10 years of successfully running it in Östersund. The Sports Technologyeducation at Mid Sweden University started at Campus Östersund in 2003 as a part of the curriculum of theEngineering Department. This specialization was initially at the three-year Bachelor level, and later it was extendedto an additional two-year Master level. Aiming at the quality of Sports Technology education, three keystones areunderlying its process, representing the solid knowledge base, capacity to be flexible in problem solving and the usean innovative approaches. The Department unites researches with a background in both natural sciences andengineering disciplines, having a wide experience of working with and within the industry, equally active in researchand teaching. The unique constellation of the profiles forming the Department include not only the SportsTech®group, being “the backbone”, but also the Ecology and Eco-technology, and Quality Technology groups bringing theexcellence and extra competence needed to assure the quality of the Sports Technology education. We were the firsthigher education institution in Sweden to give this kind of education program and now some other SwedishUniversities have followed us. Our success can be measured by a number of graduates taking good jobs in theindustry. We also enjoy a steady flow of new students coming from all parts of Sweden, and Sports Technologyeducation stays among the most desirable ones in the country.

  • 4.
    Elmer, Steven
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Development of a novel eccentric arm cycle ergometer for training the upper body2013In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 45, no 1, p. 206-211Article in journal (Refereed)
    Abstract [en]

    Several investigators have demonstrated that chronic eccentric leg cycling is an effective method for improving lower body neuromuscular function (e.g., quadriceps muscle size, strength, and mobility) in a variety of patient and athletic populations. To date, there are no reports of using eccentricarm cycling (ECarm) as an exercise modality, probably in large part because of the lack of commercially available ECarm ergometers. Purpose: Our purposes for conducting this study were to 1) describe the design and construction of an ECarm ergometer and 2) compare ECarm to traditional concentric arm cycling (CCarm). Methods: All of the parts of a Monark 891E cycle ergometer (Monark Exercise AB, Vansbro, Sweden) were removed, leaving the frame and flywheel. An electric motor (2.2 kW) was connected to the flywheel via a pulley and a belt. Motor speed and pedaling rate were controlled by a variable frequency drive. A power meter quantified power and pedaling rate, and provided feedback to the individual. Eight individuals performed 3-min ECarm and CCarm trials at 40, 80, and 120 W (60 rpm) while V̇O2 was measured. Results: The ECarm ergometer was simple to use, was adjustable, provided feedback on power output to the user, and allowed for a range of eccentric powers. V̇O2 during ECarm was substantially lower compared with CCarm (P < 0.001). At similar V̇O2 (0.97 ± 0.18 vs 0.91 ± 0.09 L•min, for ECarm and CCarm, respectively, P = 0.26), power absorbed during ECarm was approximately threefold greater than that produced during CCarm (118 ± 1 vs 40 ± 1 W, P < 0.001). Conclusion: This novel ECarm ergometer can be used to perform repetitive, high-force, multijoint, eccentric actions with the upper body at a low level of metabolic demand and may allow researchers and clinicians to use ECarm as a training and rehabilitation modality. © 2012 by the American College of Sports Medicine.

  • 5.
    Hofmann, K. B.
    et al.
    Otto Bock Healthcare Products GmbH, Vienna, Austria.
    Ohlsson, M. L.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Höök, M.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, J.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Kersting, U. G.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Aalborgs Universitet.
    The influence of sitting posture on mechanics and metabolic energy requirements during sit-skiing: a case report2016In: Sports Engineering, ISSN 1369-7072, E-ISSN 1460-2687, Vol. 19, no 3, p. 213-218Article in journal (Refereed)
    Abstract [en]

    Several different sitting postures are used in Paralympic cross-country sit-skiing. The aim of this study was to evaluate the impact of sitting posture on physiological and mechanical variables during steady-state double-poling sit-skiing, as well as to determine how seat design can be improved for athletes without sufficient trunk control. Employing a novel, custom-designed seat, three trunk positions were tested while performing double-poling with submaximal oxygen consumption on an ergometer. Cycle kinematics, pole forces, and oxygen consumption were monitored. The athlete performed best, with longer cycle length and less pronounced metabolic responses, when kneeling with the trunk resting on a frontal support. For this case, a forward leaning trunk with knees below the hip joint was interpreted as most optimal, as it showed lower oxygen consumption and related parameters of performance during cross-country sit-skiing. Further investigations should examine whether such improvement is dependent on the level of the athlete’s handicap, as well as whether it is also seen on snow.

  • 6.
    Holmberg, L. Joakim
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Ohlsson, Marie
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Musculoskeletal simulations: a complementary tool for classification of athletes with physical impairments2012In: Prosthetics and orthotics international, ISSN 0309-3646, E-ISSN 1746-1553, Vol. 36, no 3, p. 396-397Article in journal (Refereed)
  • 7.
    Kuzmin, Leonid
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Estimating surface hydrophobicity by introducing a wettability factor based on contact anglesManuscript (preprint) (Other academic)
  • 8.
    Lintzén, Nina
    et al.
    Luleå Univ. of Technology, Luleå.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Melin Söderström, Erik
    Peak Innovation, Östersund.
    Nilsson, Kajsa
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Skoglund, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Laboratory Investigation of Different Insulating Materials Used for Snow Storage2019In: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 33, no 4, article id 04019012Article in journal (Refereed)
    Abstract [en]

    Storage of snow has become of increasing interest for the winter business industry. Covering a pile of snow with an insulating material protects the snow from heat transfer from the surroundings and reduces the melting. Storing snow enables ski resorts to set an opening date, and it can also be used to secure winter sports events that are dependent on snow. Cover materials that are commonly used as insulation are wood-based materials, such as sawdust, and textile materials and sheets. How efficiently a cover material functions as thermal insulation depends on the material characteristics and thickness of the insulating layer. In this study, results from a laboratory experiment are presented, which aimed at comparing different commonly used cover materials, as well as some other materials that have not previously been used as thermal insulation on snow. Different layer thicknesses were also investigated. The results show that the insulating capacity of sawdust is reduced with time. Despite degrading insulating properties with time, sawdust is still considered one of the best materials to use as insulation on snow, and it is also more efficient than the textile materials investigated in this study. Doubling the textile layers or adding a three-dimensional (3D) spacer textile, which implies adding a layer of air between the textile and the snow, reduces the snow melting. Water absorption, water transport, and evaporation of water affect the melting. In this work, evaporative cooling did not prove to reduce melting; therefore, it was not evident whether a textile material should be permeable. An interesting material used in the study was Quartzene, which absorbed all the melt water and protected the snow most efficiently of the materials tested. 

  • 9.
    Lund Ohlsson, Marie
    et al.
    Linköpings universitet.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, Joakim
    Linköpings universitet.
    Can Simulations Assist in Classification Development?2013In: Equipment and Technology in Paralympic Sports, International Paralympic Committee , 2013Conference paper (Refereed)
  • 10.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, L. Joakim
    Linköpings Universitet.
    Descriptive comparison of three technique analysis methods in the context of cross-country sit-skiing: energy expenditure and gross efficiency, descriptive biomechanics and musculoskeletal simulationsManuscript (preprint) (Other academic)
    Abstract [en]

    In parasports, technique analysis on how impairments and equipment affects athletic performance is important for classification. The purpose of this study was to compare three quantitative technique analysis methods: energy expenditure and gross efficiency, descriptive biomechanics, and musculoskeletal simulations for two cross-country sit-skiing sitting positions. These are: 1) knees higher than hips (KH) and 2) knees lower than hips with a frontal trunk support (KL).Five able-bodied cross-country skiers performed a sub-maximal incremental test and a 3 min maximal time-trial in each sitting position. During the tests, respiration, blood lactate concentrations, 3D full-body kinematics, pole forces and electromyography were measured.All three methods complement each other and by different parameters they all indicate superior technique in KH. Descriptive biomechanics showed differences in movement pattern, larger hip and spine flexion in KH. The method of energy expenditure and gross-efficiency capture both physiology and technique, showing lower anaerobic metabolism in KH. The musculoskeletal simulations showed how different muscle groups contributed to performance, showing higher contribution from spine and less in arms for KH. This study indicated why and how performance was enhanced in the human-equipment interaction, which is important for parasport classification and competition rules.

  • 11.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Holmberg, L Joakim
    Linköping University.
    Estimation of muscle work in cross-country sit-skiing2019Conference paper (Refereed)
    Abstract [en]

    Introduction: In Nordic skiing all sitting athletes compete in the same event competition. The sitting positions differ between athletes. Most of the athletes sit knee-seated, or with their thighs tilted downward (KL) and free to move their trunk. Some athletes do not have the possibility to sit in that position and therefore adjust their sitting position. For example, athletes with reduced muscle control in hips and lower trunk sit with their knees higher than their hips (KH) to increase stability.

    Purpose: The purpose of this study was to examine how sitting position KL and KH affects the muscular power.

    Methods: One female able-bodied athlete performed one test session in each sitting position (KL and KH) comprising five times 3 minutes sub-maximal exercise and a maximal time-trial in a double-poling ergometer (ThoraxTrainer A/S, Denmark). During the tests 3D kinematics (Qualisys AB, Sweden), pole forces and power output were measured. From the measured data, participant and test specific musculo-skeletal inverse-dynamics simulation models were created using the AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark). From the simulations of submaximal exercise power output 37 W, 52 W and maximal time-trial the muscular metabolic power (mMP) was computed according to Holmberg (2013).

    Results: The power output in maximal exercise was higher in KL (90.1 W) compared to KH (74.7 W). During both submaximal and maximal exercise, the total muscular metabolic power was larger in KL compared to KH (KL mean 861 W and KH mean 682 W). The muscular metabolic power also showed larger relative involvement of legs in KL (KL mean 18 % and KH mean 4 %) and larger relative involvement of arms and trunk in KH.

    Conclusion: That sitting position KL compared to KH is related to higher performance for athletes without impairment in hips and trunk is known before (Gastaldi, 2012). However, the results from this study explains why performance is higher in KL, i.e. that larger muscular metabolic power are produced in the legs. This study also shows the size of the involvement of legs, which could be interesting for development of classification rules.

  • 12.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics. Swedish Parasport Federation.
    Holmberg, L. Joakim
    Linköping University.
    LUMBAR SPINE REACTION FORCES IN SEATED PARA-SPORT: CROSS-COUNTRY SIT-SKIING2017In: Brisbane 2017: Abstract book, 2017Conference paper (Refereed)
    Abstract [en]

    INTRODUCTION

    For wheel-chair users shoulder injuries [1] and lower back injuries [2] are common. Lower back kyphosis of the spine, increases the anterior shear force in the lower back [3] and increases the risk of shoulder injuries [4].

     

    Cross-country sit-skiing (CCSS) is an endurance sport where the athlete is seated in a sledge mounted on a pair of skis and propel themselves by poling with a pair of sticks. This sport creates more equal loading on the muscles around the shoulder than wheel-chair rolling [5] which is positive in an injury perspective for the gleno-humeral joint [1].

     

    Athletes in CCSS with reduced trunk muscle control often sits in a sledge with their knees higher than their hips (KH) and a backrest. This position is hypothesized to be associated with spinal kyphosis and hence an increased risk of injuries. Therefore we have created a new sitting position with knees lower than hips (KL) with the trunk restrained on a frontal support.

     

    The aim of this study was to compute the L4/L5 joint reactions and compare the results between the positions KH and KL.

    METHODS

    Five female abled-bodied cross-country skiing athletes (62.6 ± 8.1kg, 1.67 ± 0.05m)  performed one exercise test session in each sitting position; The sessions included a sub-maximal incremental test, including 4-6 exercise levels of 3 min (exercise intensity nr 4, 37W, reflected race-pace) and a maximal time-trial (MAX) of 3 min on a commercial skiing ergometer (ThoraxTrainer A/S, Denmark).

     

    Full-body kinematics (Qualisys AB, Sweden) and pole forces (Biovision, Germany) were measured in 200 Hz. These data served as input to inverse dynamic simulations in The AnyBody Modelling system (AMS 6.0, Anybody Technology A/S, Denmark). For each participant and sitting position, simulations were made for exercise intensity 37W and MAX over four poling cycles using a 5th order polynomial muscle recruitment criteria. Compression forces and anterior shear forces between L4 and L5 were computed and normalized to each participant’s standing joint reactions. Data were compared pair-wise between the two sitting positions.

     

    Statistical significance (p ≤ 0.05) were marked with asterisk (*). Tendency of difference (0.05 ≤ p < 0.10) were marked (ǂ).

     

    RESULTS AND DISCUSSION

    Performance was higher in position KH (KL: 0.77±0.08 W/kg, KH: 1.00±0.14 W/kg, p < 0.01). No difference were observed in cycle length or cycle time. Kinematics results showed that KL had less spine flexion and range of motion in flexion. KH showed higher mean pole force in 37W and tendency of higher peak pole force in MAX.

     

    In standing, L4/L5 compression and anterior shear forces were 354 ± 45N and 32 ± 11N respectively. The normalized L4/L5 reaction forces (fig. 1) were larger in KH, especially during MAX intensity due to higher power. For equal power output, 37W, the mean anterior shear force was larger in KH and the mean compression force showed tendency of larger in KH (p=0.077).

     

    Figure 1: Normalized joint reaction forces, compression and anterior shear forces, between vertebrae L4/L5 for the two sitting positions KH and KL with trunk restraint. Min – minimal force, Maximal force and Mean – mean force over the four poling cycles.

     

    CONCLUSIONS

    Based on inverse-dynamics musculo-skeletal simulations of 5 abled-bodied athletes, the sitting position KL with frontal restraint reduced the compression and shear force between the L4/L5 vertebrae but impeded performance. This study shows the difficulty of comparing performance and safety in the same piece of equipment.

     

    ACKNOWLEDGEMENTS

    The authors acknowledge the Rolf & Gunilla Enström foundation and the Promobilia foundation, Sweden, for financial support, and the Ableway AB (Sweden) for construction of the sledges.

     

    REFERENCES

    1. Burnham RS, et al., Am J Sports Med, 21: 238-242, 1993.
    2. Thyberg M, et al., Disabil rehabil. 23:677-682, 2001.
    3. McGill SM, et al., Clin Biomech, 15: 777-780, 2000.
    4. Samuelsson KA, et al., J Rehabil Res Dev, 41: 65-74, 2004.
    5. Bjerkefors A, et al., Int J Sports Med, 34: 176-182, 2013.
  • 13.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Holmberg, L. Joakim
    Linköpings Universitet.
    Shoulder and Lower Back Joint Reaction Forces in Seated Double Poling2018In: Journal of Applied Biomechanics, ISSN 1065-8483, E-ISSN 1543-2688, Vol. 34, no 5, p. 369-376Article in journal (Refereed)
    Abstract [en]

    Overuse injuries in the shoulders and lower back are hypothesized to be common in cross-country sit-skiing. Athletes with reduced trunk muscle control mainly sit with the knees higher than the hips (KH). To reduce spinal flexion, a position with the knees below the hips (KL) was enabled for these athletes using a frontal trunk support. The aim of the study was to compare the shoulder joint (glenohumeral joint) and L4-L5 joint reactions of the KL and KH sitting positions. Five able-bodied female athletes performed submaximal and maximal exercise tests in the sitting positions KL and KH on a ski ergometer. Measured pole forces and 3-dimensional kinematics served as input for inverse-dynamics simulations to compute the muscle forces and joint reactions in the shoulder and L4-L5 joint. This was the first musculoskeletal simulation study of seated double poling. The results showed that the KH position was favorable for higher performance and decreased values of the shoulder joint reactions for female able-bodied athletes with full trunk control. The KL position was favorable for lower L4-L5 joint reactions and might therefore reduce the risk of lower back injuries. These results indicate that it is hard to optimize both performance and safety in the same sit-ski.

  • 14.
    Lund Ohlsson, Marie
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Stöggl, T.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Asymmetry case study during skiing in the diagonal stride using a lower leg prosthesis2012Conference paper (Refereed)
  • 15.
    Roos, Stefan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Botero Vega, Carlos Alberto
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Koptioug, Andrei
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Macro- and Micromechanical Behavior of 316LN Lattice Structures Manufactured by Electron Beam Melting2019In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 28, no 12, p. 7290-7301Article in journal (Refereed)
    Abstract [en]

    This work focuses on the possibility of processing stainless steel 316LN powder into lightweight structures using electron beam melting and investigates mechanical and microstructural properties in the material of processed components. Lattice structures conforming to ISO13314:2011 were manufactured using varying process parameters. Microstructure was examined using a scanning electron microscope. Compression testing was used to understand the effect of process parameters on the lattice mechanical properties, and nanoindentation was used to determine the material hardness. Lattices manufactured from 316L using EBM show smooth compression characteristics without collapsing layers and shear planes. The material has uniform hardness in strut shear planes, a microstructure resembling that of solid 316LN material but with significantly finer grain size, although slightly coarser sub-grain size. Grains appear to be growing along the lattice struts (e.g., along the heat transfer direction) and not in the build direction. Energy-dispersive x-ray spectroscopy analysis reveals boundary precipitates with increased levels of chromium, molybdenum and silicon. Studies clearly show that the 316LN grains in the material microstructure are elongated along the dominating heat transfer paths, which may or may not coincide with the build direction. Lattices made from a relatively ductile material, like 316LN, are much less susceptible to catastrophic collapse and show an extended range of elastic and plastic deformation. Tests indicate that EBM process for 316LN is stable allowing for both solid and lightweight (lattice) structures.

  • 16.
    Roos, Stefan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Koptioug, Andrei
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Characterization of 316ln lattice structures fabricated via electron beam melting2017In: Materials Science and Technology Conference and Exhibition 2017, MS and T 2017, Association for Iron and Steel Technology, AISTECH , 2017, p. 336-343Conference paper (Refereed)
    Abstract [en]

    One of the promising application areas of additive manufacturing (AM) relates to light weight structures, including complex near net shape geometries and lattices. So far one of the limiting factors hampering wider industrial usage of AM technologies is the limited availability of processed materials. The aim of present study was to expand the previous success in electron beam melting (EBM®) manufacturing of 316LN bulk materials into thinner lattice structures thus further widening the application areas available for the method. Present paper reports on the initial results where lattice structures with octagonal basic cells were manufactured using EBM® and characterized using microscopy and compression testing. 

  • 17.
    Skoglund, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Lower Leg Prosthesis for Cross-Country Skiing Classical Technique2013Conference paper (Refereed)
  • 18.
    Swarén, Mikael
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Holmberg, Hans-Christer
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Acceleration of the head during alpine skiing2010In: Proceedings for the fifth international conference on Science and Skiing / [ed] Erich Mueller, Salzburg, 2010, p. 82-Conference paper (Refereed)
  • 19.
    Wedeking, Daniela
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Swarén, Mikael
    Swedish Olympic Academy, KTH Royal Institute of Technology, Stockholm, Sweden.
    Danvind, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Management and Mechanical Engineering.
    Lund Ohlsson, Marie
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    The influence of arm and ski pole during alpine skiing2019Conference paper (Refereed)
    Abstract [en]

    INTRODUCTION: Research investigating the correlation between impairment and key performance indicators in para-alpine skiing is needed for a future evidence based classification system (Tweedy and Vanlandewijck 2011). Only a little research in para-alpine skiing exists, especially in the standing classes LW5/7 and LW6/8 (impairment of one or two arms). The use of arms and poles affects performance in alpine skiing[OM1]  but how underlying biomechanical parameters as kinematics and kinetics are related to performance has to the authors knowledge not been studied before.

    PURPOSE: The purpose of this study was to further the understanding of slalom skiing with two ski poles, one pole or without poles (c2, c1, c0) by investigating the biomechanical differences (kinematics and foot plantar pressure) for able-bodied athletes.

    METHODS: Ten able-bodied right-handed junior skiers on national level were tested in three conditions - c0, c1, c2, while skiing a slalom course (28 gates, 62 m vertical drop). 3D kinematic data were collected at 200 Hz by 12 inertial motion units (Myomotion, Noraxon Inc, USA) placed on head, trunk, pelvis, arms and legs. Ski-time was measured with timing gates (XS Crystal Synchronization, Brower Timing Systems, USA) and kinetics were measured with pressure insoles (Pedar, Novel GmbH, Germany) placed inside each ski boot. Normal ground reaction force (nGRF) and relative force time integrals (relFTI) were calculated according to Melai et. Al (2011). Kinematics and plantar pressure were analysed over three right and left turns and averaged for each condition. Right turn and left turn were distinguished at the time point where the shank was standing vertical.

    RESULTS: Time analysis showed that time increased with the use of less ski poles, mean difference between c1c2 of 1.27 ± 1.69 s (p=0.001) and between c0c1 of 0.73 ± 1.95 s (p=0.003[OM2] ). Kinematic analysis showed that different approaches were used to attack a slalom gate in condition c1 and c0, for example slalom-attack, giant slalom attack or opposite arm attack. Interquartile range and median of the body angles [OM3] differed between conditions, e.g. lower median (indicate less deviation from anatomical  basic position[OM4] ) in c0 and mostly lower than in c1 and c2. Furthermore, relFTI was related to the turning side (right or left turn) and showed largest asymmetry for condition c1.

    CONCLUSION: Reduced balance due to missing ski pole/s lead to compensatory movements in the upper body and asymmetry in foot plantar pressure. This reduced the ability for a controlled turn. Whether or not only reduced balance or also the skiers low experience of skiing with reduced number of poles influenced the performance remains unclear.

    REFERENCES

    Melai, Tom, T. Herman IJzerman, Nicolaas C. Schaper, Ton L.H. de Lange, Paul J.B. Willems, Kenneth Meijer, Aloysius G. Lieverse, and Hans H.C.M. Savelberg. 2011. ‘Calculation of Plantar Pressure Time Integral, an Alternative Approach’. Gait & Posture 34 (3): 379–83. https://doi.org/10.1016/j.gaitpost.2011.06.005.

    Tweedy, S. M., and Y. C. Vanlandewijck. 2011. ‘International Paralympic Committee Position Stand--Background and Scientific Principles of Classification in Paralympic Sport’. British Journal of Sports Medicine 45 (4): 259–69. https://doi.org/10.1136/bjsm.2009.065060.

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